1999 "E"450 SuperDuty Air Intake??

Have you looked at E Bay?

It should be the same part used with all gas engines in the E-series, from 1997 forward. My V-10 2003 E-450 and 5.4 V-8 2012 E-350 use the same round filter in the same round box behind the radiator. I know the filter itself has not changed.

It might also be used in F-series V-8 and V-10 installations, but I'm not sure of that, haven't bought any full size Ford pickups.

K&N has a replacement cold air intake, if you want to take your chances on lesser filtration for better air flow. They use a re-usable oil-wetted filter, the box is entirely open, which goes way beyond cutting an opening in the intake side of the OEM box. That is also the same part for 5.4 or 6.8 E-series. List price for the intake system is almost $700, but it can be bought for a bit more than half of that.

Ford had a "badging" problem in the late 1990's. E350 had been around for decades, then Ford wanted more GVWR. They brought out what is now known as E450, but for a few years they badged it "E-SuperDuty" and that sounds like what you have. If the GVWR in the door jam label is 14050-pounds, its E-SuperDuty. Then Ford called all the bigger vans, cutaways, cube vans, etc "Super Duty" So, E350 Super Duty, E450 Super Duty, etc.
I'm sure parts from a van or truck close to your model year, with the same engine type (V10) would work fine.

Several items on my 1 ton (not 450) that are GVWR specific. Because of the build of MH, it is a lot bigger GVW. Part places think everybody has GVW a lot less than what they sell most often. Example is Brake lines etc. I now take my VIN number in with me.

But very few engine parts are VIN specific.

Seems like previous owner was trying to get a little bit more horsepower out of it. There is a mode that you can replace air intake pipe from the grill and replace with bigger pipe. Or people drill 1 1/2 inch holes, so more air available. I think you get about 10 or 15 more HP out of it. Nothing to brag about.

If you're not peculiar, just glue on some more plastic.

Whatever you do, Just make sure all air is being filtered before it hits the engine.

The OEM one is adequate ... check with your local boneyard to see if they have a used one. They should have as they almost never wear out unless tampered with.

Perhaps and alternate is the AIS air intake system. It is a HD version available from FORD for their F-series trucks. I don't know if they make them for the E-series.

A good place to check will be over at the Ford Truck Enthusiast forum. Great knowledge base .... that's where I went when we used to have our Class C.

Hope this helps. ~ BugJr ~